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Stimulation of human lymphocytes with phytohemagglutinin is known to induce an increase in overall DNA polymerase activity (DNA nucleotidyltransferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7). Previous work [Pedrali Noy, G., Dalpra, L., Pedrini, A. M., Ciarrocchi, G., Giulotto, E., Nuzzo, F. & Falaschi, A. (1974) Nucleic Acids Res. 1, 1183] has shown that two subsequent waves of induction of DNA polymerase can be observed in this system; a first wave occurs in parallel with the increase in DNA replication rate; a second one occurs when the DNA synthesis rate is returned to minimal levels; the second peak is parallel to a maximum in DNA ligase and DNase levels.In the present work we have measured the levels of the DNA polymerases-a and -, in phytohemagglutinin-stimulated lymphocytes during a 12-day period; both enzymes are present at detectable levels at time zero; in correspondence to the peak of DNA synthesis rate (between the fourth and fifth day) a peak of DNA polymerase-a is observed, increasing by a factor of approximately 20-fold over the zero time value; subsequently, the level of DNA polymerase-a decreases in parallel with DNA synthesis rate. The DNA polymerase-ft is also increased in correspondence to the peak in DNA synthesis rate, but reaches its maximum at later times, between the eighth and tenth day of incubation.The capacity of stimulated lymphocytes to perform repair synthesis following UV damage was measured in the same cells used for the enzyme activity determinations; this capacity also shows two maxima: a first one correlated with the peak in DNA replication rate, and a second one correlated with the peak of DNA polymerase-fl.These data suggest a certain tendency to the specialization of functions in human cell DNA polymerases; the a-enzyme seems mainly correlated with DNA replication, whereas the a-enzyme seems more correlated with the ability of the cell to perform repair type synthesis.Human lymphocytes stimulated with phytohemagglutinin (PHA) represent a useful model system to obtain information on the role of the enzymes of DNA metabolism; the stimulated cells undergo dramatic variations in DNA replication rate (1), and any positively correlated variation of the level of a certain enzyme gives a strong inference for a function of that enzyme in DNA replication.Several authors have shown that overall DNA polymerase (DNA nucleotidyltransferase; deoxynucleosidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7) levels increase markedly in parallel to DNA synthesis rate, and both parameters reach their maximum at the same time, between the second and fifth day of culture (2-6), in correspondence to the peak of mitoses. In human cells two main molecular species of DNA polymerase are known, defined as -a and -,3 (7-10); the a-enzyme is the most abundant one, has an s°20,w of 6.5 S and is inhibited by N-ethylmaleimide; the ,B-enzyme has an S020W of 3.4 S and is insensitive to N-ethylmaleimide. The molecular species of DNA polymerase which is mainl...

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2-Geranylgeranyl-1,4-dihydroxybenzene [1] and a mixture of fatty acid esters of this phenol were isolated from the fruiting bodies of Lactarius lignyotus. Compound 1 was highly active in the brine shrimp test and showed significant inhibitory activity on DNA, RNA, and protein synthesis in HeLa and HL-60 cell lines.